Moisture barriers for paper materials

ABSTRACT

Provided herein is a tobacco packaging material, comprising a paper material coated with at least one polymer layer. The polymer layer comprises at least one repulpable polymer, and wherein the tobacco packaging material has a water vapor transmission rate (WVTR) that is at least 90% lower than the paper material. Further provided is a tobacco package comprising the tobacco packaging material, wherein the tobacco package is substantially free of any foil inner liner or polypropylene film. Further described is a method for making the tobacco packaging material, comprising extrusion coating at least one repulpable polymer onto a paper material to form a polymer layer, and optionally further depositing at least one atomic layer deposition (ALD) layer that comprises a metal oxide.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/543,568 filed Nov. 17, 2014, the content of which is herebyincorporated by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to a tobacco packaging material. Inparticular, the present disclosure relates to a tobacco packagingmaterial comprising a paper material coated with at least one repulpablepolymer layer and optionally at least one layer deposited by atomiclayer deposition (ALD).

DISCLOSURE OF RELATED ART

Tobacco product packages and materials used to construct packagedcigarettes are known in the art. Typically, overwrap materials are usedin tobacco product packages. Suitable overwrap materials includepolypropylene films, such as films characterized as “cellophane-typefilms” that traditionally have been employed for wrapping packagedcigarettes. See, for example, the types of overwrap materials describedin U.S. Pat. No. 5,139,140 to Burrows et al. and U.S. Pat. No. 5,542,529to Hein, III et al., each of which is incorporated herein by reference.

The outer wrapping material assembly can be equipped with tear tape.See, for example, U.S. Pat. No. 4,717,017 to Sprinkel, Jr. et al.; U.S.Pat. No. 4,836,378 to Lephardt; U.S. Pat. No. 5,192,262 to Amendola etal.; U.S. Pat. No. 5,595,803 to May et al.; and U.S. Pat. No. 7,118,792to Hewitt et al.; each of which is incorporated herein by reference.Representative types of tear tape materials suitable for use inassociation with other cigarette packaging materials are available fromcommercial sources such as Arlin Mfg. Co., Inc. and P. P. Payne Limited.

Additional cigarette packages and packaged cigarettes are described in,for example, U.S. Pat. No. 4,852,734 to Allen; U.S. Pat. No. 5,139,140to Burrows; U.S. Pat. No. 5,333,729 to Wolfe; U.S. Pat. No. 5,542,529 toHein; U.S. Pat. No. 8,522,515 to Carter; U.S. Pat. No. 8,118,161 toGuerrera et al.; U.S. Pat. No. 8,783,454 to Igo; WO/2011/076405 to Igo;WO/2014/128037 to Pilzecker; WO/2014/128264 to Pilzecker; and EP2769930A to Pilzecker; each of which is incorporated herein byreference.

However, because prior art tobacco product packages usually includeeither a foil inner liner or a polypropylene film to protect tobaccosfrom moisture loss, they cannot be directly recycled and thus are notenvironmentally friendly. It would be desirable to provide a tobaccopackage that is fully recyclable, which should be substantially free ofany foil inner liner or polypropylene film while still capable ofprotecting tobaccos from moisture loss.

SUMMARY

The above and other needs are met by aspects of the present disclosurewhich, in a first aspect, provides a tobacco packaging material,comprising a paper material coated with at least one polymer layer,wherein the polymer layer comprise at least one repulpable polymer, andwherein the tobacco packaging material has a water vapor transmissionrate (WVTR) that is at least 90% lower than the paper material.

In some embodiments, the tobacco packaging material further comprises atleast one ALD layer, wherein the ALD layer comprises a metal oxide. Insome embodiments, the tobacco packaging material has a WVTR of 10g/m²/day or less at 38° C. and 90% RH.

In second aspect, a tobacco package is provided, wherein the tobaccopackage comprises the tobacco packaging material described herein and issubstantially free of any foil inner liner (e.g., Aluminum foil) orpolypropylene film (e.g., OPP film).

In a third aspect, a method for making a tobacco packaging material isprovided, comprising extrusion coating at least one repulpable polymeronto a paper material to form a polymer layer, wherein the tobaccopackaging material has a WVTR that is at least 90% lower than the papermaterial.

In some embodiments, the method further comprises heat treating thepaper material coated with the polymer layer. In some embodiment, themethod further comprises depositing at least one ALD layer onto thepaper material coated with the polymer layer, wherein the ALD layercomprises a metal oxide.

Further features and advantages of the present disclosure are set forthin more detail in the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described the disclosure in general terms, reference willnow be made to the accompanying drawings, which are not necessarilydrawn to scale, and wherein:

FIG. 1 shows: (A) a top view image of uncoated paperboard (Mag=500×);(B) a top view image of polylactic acid (PLA) coated paperboard(Mag=500×); (C) a top view image of the PLA-paperboard interface(Mag=500×); and (D) a cross-sectional image of the PLA coating onpaperboard (Mag=100×).

FIG. 2 shows WVTR (at 50% or 90% RH, 23° C.) results of plain paper andboard substrates.

FIG. 3 shows PLA amounts of each extrusion coating recipe.

FIG. 4 shows a WVTR (at 90% RH, 23° C.) comparison of 90° folded andnon-folded PLA coated paper and board.

FIG. 5 shows WVTR (at 50% or 90% RH, 23° C.) results of PLA extrusioncoated paper and board substrates.

FIG. 6 shows a WVTR (at 90% RH, 23° C.) comparison of 90° folded andnon-folded PGA coated paper and board.

FIG. 7 shows WVTR (at 50% or 90% RH, 23° C.) results of PGA extrusioncoated paper and board.

FIG. 8 shows WVTR (at 90% RH, 23° C.) results of heat treated non-foldedand folded PGA extrusion coated board.

FIG. 9 shows WVTR (at 90% RH, 23° C.) results of 90° folded andnon-folded ALD Al₂O₃ coated PLA paper and board.

FIG. 10 shows WVTR (at 50% or 90% RH, 23° C.) results of ALD A1203coated PLA paper and board.

FIG. 11 shows WVTR (at 90% RH, 23° C.) results of 90° folded andnon-folded ALD Al₂O₃ coated PGA paper and board.

FIG. 12 shows WVTR (at 50% or 90% RH, 23° C.) results of ALD Al₂O₃coated PGA paper and board.

FIG. 13 shows WVTR (at 90% RH, 23° C.) results of 90° folded andnon-folded ALD hybrid coated PLA paper and board.

FIG. 14 shows WVTR (at 50% or 90% RH, 23° C.) results of ALD hybridcoated PLA paper and board.

FIG. 15 shows WVTR (at 90% RH, 23° C.) results of 90° folded andnon-folded ALD hybrid coated PGA paper and board.

FIG. 16 shows WVTR (at 50% or 90% RH, 23° C.) results of ALD hybridcoated PGA paper and board.

DETAILED DESCRIPTION OF THE DISCLOSURE

The present disclosure now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allaspects of the disclosure are shown. Indeed, the disclosure may beembodied in many different forms and should not be construed as limitedto the aspects set forth herein; rather, these aspects are provided sothat this disclosure will be thorough and complete, will fully conveythe scope of the disclosure to those skilled in the art, and willsatisfy applicable legal requirements. Like numbers refer to likeelements throughout. As used in this specification and the claims, thesingular forms “a,” “an,” and “the” include plural referents unless thecontext clearly dictates otherwise.

Tobacco Packaging Material

In various embodiments, the invention described herein relates to atobacco packaging material comprising a paper material coated with atleast one polymer layer, wherein the polymer layer comprise at least onerepulpable polymer.

The paper material can be, for example, any commercial paper and boardsubstrate that are suitable for making tobacco packages. In oneembodiment, the paper material is a paper having a base weight of 20-200g/m². In another embodiment, the paper material is a paper having a baseweight of 50-150 g/m². In a further embodiment, the paper material is aboard having a base weight of 100-500 g/m². In another embodiment, thepaper material is a board having a base weight of 200-300 g/m².

The paper material can comprise, for example, one or more additives. Inone embodiment, the additive is nanocellulose based materials. In oneembodiment, the additive is cellulose nanofibrils (CNF). In oneembodiment, the additive is cellulose nanocrystals (CNC).

Repulpable polymers refer to polymers that can be repulped and,therefore, directly recyclable without having to be separated from thepaper materials of tobacco packages. As a result, the repulpablepolymer-coated paper material described herein is more environmentallyfriendly than polymer materials currently used in tobacco packages, suchas polypropylene. The repulpable polymers can be, for example,biodegradable. In one embodiment, the repulpable polymer is polyglycolicacid (PGA). In another embodiment, the repulpable polymer is polylacticacid (PLA). In a further embodiment, the repulpable polymer ispolyhydroxyalkanoate (PHA).

In one embodiment, the paper material is coated with a single polymerlayer, such as an amorphous polymer layer or a semi-crystalline polymerlayer. In another embodiment, the polymer is coated with multiplepolymer layers, such as at least two polymer layers or at least threepolymer layers. The multiple polymer layers can comprise, for example,the same polymer. The multiple polymer layers can comprise, for example,different polymers. The multiple polymer layers can comprise, forexample, two layers each comprising the same polymer but with differentcrystallinity.

In one embodiment, the paper material is coated with at least oneamorphous polymer layer and at least one semi-crystalline polymer layer.In another embodiment, the paper material is coated with at least twoamorphous polymer layers and at least one semi-crystalline polymerlayer. In a further embodiment, the paper material is coated with atleast one amorphous polymer layer and at least two semi-crystallinepolymer layers. In one embodiment, the paper material is coated with anamorphous polymer layer as the bottom layer directly in contact with thepaper material. In another embodiment, the paper material is coated witha semi-crystalline polymer layer as the bottom layer directly in contactwith the paper material. In one embodiment, the paper material is coatedwith more than one layer, with the top layer being an amorphous polymerlayer. In another embodiment, the paper material is coated with morethan one layer, with the top layer being a semi-crystalline polymerlayer.

In one embodiment, the paper material is coated with about 1-100 g/m² ofpolymers. In another embodiment, the paper material is coated with about10-300 g/m² of polymers. In another embodiment, the paper material iscoated with about 20-200 g/m² of polymers. In a further embodiment, thepaper material is coated with about 30-100 g/m² of polymers.

In some embodiments, the paper material coated with the polymer layer isheat treated to increase crystallinity.

The tobacco packaging material can further comprise, for example, atleast one inorganic ALD layer. The ALD layer can comprise, for example,a metal oxide. More specifically, the ALD layer can comprise, forexample, Al₂O₃ or SiO₂. In addition to the inorganic material, the ALDlayer can further comprise, for example, an organic material. In oneembodiment, the ALD layer has a thickness of 1-500 nm. In anotherembodiment, the ALD layer has a thickness of 2-200 nm. In a furtherembodiment, the ALD layer has a thickness of 5-100 nm.

In some embodiments, the tobacco packaging material comprises at leasttwo ALD layers. In some embodiments, the tobacco packaging materialcomprises a partially organic bottom layer and an inorganic top layer.The inorganic top layer can comprises, for example, Al₂O₃ or SiO₂, forimproving the barrier properties of the tobacco packaging material. Thepartially organic bottom layer can comprises, for example, a metal oxideand an elastic organic material, to provide elasticity to the whole ALDlayer structure and improve cracking behavior of the top inorganiclayer.

In one embodiment, the WVTR of the tobacco packaging material is atleast 70% lower than the WVTR of the paper material without any polymerlayer or ALD layer. In another embodiment, the WVTR of the tobaccopackaging material is at least 90% lower than the WVTR of the papermaterial without any polymer layer or ALD layer. In a furtherembodiment, the WVTR of the tobacco packaging material is at least 95%lower than the WVTR of the paper material without any polymer layer orALD layer. In yet another embodiment, the WVTR of the tobacco packagingmaterial is at least 98% lower than the WVTR of the paper materialwithout any polymer layer or ALD layer. In yet a further embodiment, theWVTR of the tobacco packaging material is at least 99% lower than theWVTR of the paper material without any polymer layer or ALD layer.

In one embodiment, the tobacco packaging material has a WVTR of 20g/m²/day or less at 38° C. and 90% RH. In another embodiment, thetobacco packaging material has a WVTR of 10 g/m²/day or less at 38° C.and 90% RH. In still another embodiment, the tobacco packaging materialhas a WVTR of 5 g/m²/day or less at 38° C. and 90% RH. In a furtherembodiment, the tobacco packaging material has a WVTR of 3.4 g/m²/day orless at 38° C. and 90% RH. In a further embodiment, the tobaccopackaging material has a WVTR of 2 g/m²/day or less at 38° C. and 90%RH.

In one embodiment, the tobacco packaging material has a WVTR of 10g/m²/day or less at 38° C. and 50% RH. In another embodiment, thetobacco packaging material has a WVTR of 5 g/m²/day or less at 38° C.and 50% RH. In a further embodiment, the tobacco packaging material hasa WVTR of 4 g/m²/day or less at 38° C. and 50% RH. In yet anotherembodiment, the tobacco packaging material has a WVTR of 3 g/m²/day orless at 38° C. and 50% RH. In yet a further embodiment, the tobaccopackaging material has a WVTR of 2 g/m²/day or less at 38° C. and 50%RH.

In one embodiment, the tobacco packaging material has a WVTR of 20g/m²/day or less at 23° C. and 90% RH. In another embodiment, thetobacco packaging material has a WVTR of 10 g/m²/day or less at 23° C.and 90% RH. In a further embodiment, the tobacco packaging material hasa WVTR of 5 g/m²/day or less at 23° C. and 90% RH. In yet anotherembodiment, the tobacco packaging material has a WVTR of 4 g/m²/day orless at 23° C. and 90% RH. In yet a further embodiment, the tobaccopackaging material has a WVTR of 3 g/m²/day or less at 23° C. and 90%RH.

In one embodiment, the tobacco packaging material has a WVTR of 10g/m²/day or less at 23° C. and 50% RH. In another embodiment, thetobacco packaging material has a WVTR of 5 g/m²/day or less at 23° C.and 50% RH. In a further embodiment, the tobacco packaging material hasa WVTR of 4 g/m²/day or less at 23° C. and 50% RH. In yet anotherembodiment, the tobacco packaging material has a WVTR of 3 g/m²/day orless at 23° C. and 50% RH. In yet a further embodiment, the tobaccopackaging material has a WVTR of 2 g/m²/day or less at 23° C. and 50%RH.

In one embodiment, the WVTR of the tobacco packaging material issubstantially unaffected by 90° folding.

In some embodiments, the invention described herein relates to a tobaccopackage comprising the tobacco packaging material. Because the tobaccopackaging material described herein has excellent barrier properties(e.g., WVTR), the tobacco package made therefrom need not include a foilinner liner (e.g., Aluminum foil) or a polypropylene film (e.g., OPPfilm). Hence, in one embodiment, the tobacco package is substantiallyfree of any foil inner liner or polypropylene film. In anotherembodiment, the tobacco package is totally free of any foil inner lineror polypropylene film.

Method for Making Tobacco Packaging Material

The present invention described herein also relates to a method formaking a tobacco packaging material, comprising extrusion coating atleast one repulpable polymer onto a paper material to form a polymerlayer, wherein the tobacco packaging material has a WVTR that is atleast 90% lower than the paper material.

The method can comprise, for example, extrusion coating a single polymerlayer onto the paper material, such as an amorphous polymer layer or asemi-crystalline polymer layer. The method can comprise, for example,extrusion coating multiple polymer layers onto the paper material, suchas at least two polymer layers or at least three polymer layers. Themultiple polymer layers can comprise, for example, the same polymer. Themultiple polymer layers can comprise, for example, different polymers.The multiple polymer layers can comprise, for example, two layers eachcomprising the same polymer but with different crystallinity.

The method can comprise, for example, extrusion coating at least oneamorphous polymer layer and at least one semi-crystalline polymer layeronto the paper material. The method can comprise, for example, extrusioncoating at least two amorphous polymer layers and at least onesemi-crystalline polymer layer onto the paper material. The method cancomprise, for example, extrusion coating at least one amorphous polymerlayer and at least two semi-crystalline polymer layers onto the papermaterial. The method can comprise, for example, extrusion coating anamorphous polymer layer as the bottom layer directly in contact with thepaper material. The method can comprise, for example, extrusion coatinga semi-crystalline polymer layer as the bottom layer directly in contactwith the paper material. The method can comprise, for example, extrusioncoating an amorphous polymer as the top layer above another polymerlayer. The method can comprise, for example, extrusion coating asemi-crystalline polymer as the top layer above another polymer layer.

The extrusion coated polymer layer can be, for example, heat treated toincrease crystallinity. In one embodiment, the extrusion coated polymerlayer is heat treated at 50-200° C. for 0.1-5 hours. In anotherembodiment, the extrusion coated polymer layer is heat treated at80-150° C. for 0.5-2 hours.

The method can comprise, for example, depositing at least one ALD layeronto the paper material coated with the polymer layer. The method cancomprises, for example, depositing at least two ALD layer onto the papermaterial coated with the polymer layer. The ALD layer can comprises, forexample, an inorganic material. The inorganic material can be, forexample, metal oxide. The ALD layer can comprise, for example, Al₂O₃. Inone embodiment, the Al₂O₃ layer is prepared using trimethylaluminum(TMA) and ozone oxidation. In another embodiment, the Al₂O₃ layer isprepared using TMA and water as an oxygen source. The ALD layer cancomprise, for example, SiO₂. In addition to the inorganic material, theALD layer can further comprise, for example, an organic material. In oneembodiment, the hybrid inorganic/organic ALD layer is prepared using TMAand ethylene glycol (EG).

In one embodiment, the ALD layer has a thickness of 1-500 nm. In anotherembodiment, the ALD layer has a thickness of 2-200 nm. In a furtherembodiment, the ALD layer has a thickness of 5-100 nm.

WORKING EXAMPLES

In the working examples, the suitability of polymer-coated paper andboard as replacements for current tobacco packaging material, e.g.polypropylene (PP) and Aluminum (Al) foil, was evaluated. Specifically,barrier coatings were coated onto two different substrates, one paperand one board substrates. Substrates were supplied in reel-form of width30 cm. Substrates were firstly coated in the extrusion roll to rollcoating line with two different polymers polyglycolic acid (PGA) andpolylactic acid (PLA). The extrusion coatings significantly improvedwater vapor transmission rate (WVTR) barrier properties of the coatedbase substrate. In addition, atomic layer deposition (ALD) thin filmcoating was applied onto extrusion coated polymers to further enhancebarrier properties. Two different types of ALD coatings were tested,inorganic alumina (Al₂O₃) coating and hybrid organic/inorganic coating.The barrier level target was 1 g/m2/day in 90% relative humidity (RH)and in temperature of 23° C., which could be achieved by combining twocoating methods. The WVTR barrier target level was also achieved afterthe samples have been subjected to the 90° folding process, which wouldtest the packaging process sustainability of the barrier properties.WVTR barrier values were measured before and after folding process toassess the effect of folding treatment on the barrier properties of thecoated material. Dry cup method (ISO 2528:19958E) was used in thebarrier measurements. At least three parallel WVTR measurements wereconducted, in the measurement of each test point. Crease and foldingtreatments were applied to the machine direction (MID) of the samplesubstrates.

Example 1—WVTR Results of Plain Paper and Board Substrates

Paper and board substrates with basis weights of 80 and 237 g/m2,respectively, were delivered by Reynolds Tobacco Company. WVTR wasmeasured at 50%/23° C. and 90%/23° C. from both materials before anycoating treatment in order to obtain a reference points which can beused as a benchmark in the assessment of the coating treatment effect inWVTR performance. WVTR results for plain paper and board substrate areshown in FIG. 2. As seen in the results, the permeability values werevery high without any coating treatment.

Example 2—WVTR Results of PLA Extrusion Coated Substrates

Two different PLA grades were used in the extrusion coating recipes:semi-crystalline PLA (NatureWorks, 4032D) and amorphous PLA (NatureWorks4060D). Three different extrusion coating recipes were used. The firstcoating recipe includes only one semi-crystalline PLA (SCP) coatinglayer, extrusion coated onto base substrates. The second recipe includesa two-layer structure, comprising a SCP layer and an amorphous PLA (AP)layer as the bottom layer and the top layer, respectively. The thirdrecipe includes a three-layer structure, comprising AP, SC and AP, inbottom to top order. The amorphous PLA layer is considered to givebetter adhesion to the base material and better heat sealing properties,while the semi-crystalline PLA is considered to be a better grade interms of barrier properties. Each coating structure was used for coatingboth substrates. The coating amount of each recipe is shown in FIG. 3.

It is evident, from the FIGS. 3 and 4, that the thicker coating resultedin lower WVTR permeability values.

A significant improvement in barrier properties was achieved for all PLAcoated materials. Barrier values for two-layer and three-layerstructures for both substrates are around 40 g/m2/day with somevariation after 90° folding. This was a significant improvement comparedto the initial WVTR of uncoated materials, which were around 1200 and820 g/m2/day for paper and board, respectively. More significantly, thebarrier properties did not seem to deteriorate after the foldingprocess, compared to non-folded samples.

All coated materials formed strong heat sealed bonds at a temperature of130°, though differences in heat sealing properties are likely at lowertemperatures and shorter heat sealing times. Coating amorphous PLA asthe uppermost layer likely resulted in better heat sealing properties atlower temperatures and shorter heat sealing times. The measured barriervalues for non-folded and folded samples at 50% and 90% RH are shown inFIG. 5.

In the multilayer coatings of which the bottom surface is amorphous(A+SC+A), the adhesion of the coating was slightly better and not soeasily delaminated away from the base material. PLA adhesion in the basematerial could be improved by optimizing the parameters of extrusioncoating process (e.g. extrusion temperature).

Example 3—WVTR Results of PGA Extrusion Coated Substrates

PGA coating amounts were 48 and 49 g/m2 for paper and board,respectively. Kuredux PGA grade by Kureha Corporation was used in thecoating trials. A significant improvement in barrier properties of PGAcoated board and paper was achieved. WVTR results at 90% RH were around15 g/m2/day with some variation for a 90° folded PGA board. For PGAcoated paper, WVTR values of less than 2 g/m2/day were recorded, asshown in FIG. 6. In addition, measured barrier values at 50% and 90% RHfor non-folded and folded samples are shown in FIG. 7.

The PGA adhesion was weak onto both paper and board substrates. As wasthe case of PLA adhesion, PGA adhesion onto the base material, could beimproved by optimizing the parameters of extrusion coating process (e.g.extrusion temperature).

Improved WVTR Results of Oven Heat Treated PGA Extrusion Coated Board

Because PGA coated board did not reach the same low permeability valuesas the corresponding PGA coated paper samples, it was attempted tofurther improve the permeability properties by one hour oven heattreatment at a temperature of 100° C. Heat treatment improved the WVTRpermeability properties of the PGA coated board as can been seen in theFIG. 8 for 90° folded samples. Values as low as PGA coated paper wereachieved for PGA coated board as well, around 2 g/m2/day at 90% RH. Suchimprovement could be explained by further crystallization of the PGAcoating, due to heat exposure, and as a result better WVTR permeabilityproperties. This may be explained by the fact that extrusion coated PGAdid not get crystallized so effectively in the coating process of boardbecause the board's higher basis weight, compared to paper. Board'sgreater mass could take away the heat needed in the crystallizationchange of a PGA coating.

Example 4—WVTR results of Al₂O₃ ALD Coating Onto Extrusion CoatedSubstrates

Al₂O₃ ALD Coating Onto PLA Coated Substrates

ALD Al₂O₃ coating was prepared in one hundred degrees centigrade usingtrimethylaluminum (TMA) and ozone oxidation. The thickness of the Al₂O₃coating, measured on the surface of a silicon wafer, was 25 nm.Determination of the true thickness of ALD coating on the PLA and PGAcoated paper and board was not possible, as a feasible technology to dosuch a measurement does not exist. Average as well as minimum andmaximum measured WVTR (90%/)23° results for non-folded and folded Al₂O₃coated PLA substrates are shown in FIG. 9. For comparison, results ofthe PLA coated paper and board without Al₂O₃ coatings are also includedin FIG. 9.

Al₂O₃ coating significantly improved the WVTR results compared to thesamples without the coating. Parallel measurements show quite highvariation, and interestingly the lowest individual measurement (3.2g/m2/day) were made for 90° folded PLA paper sample. Based on theresults, it is evident that the Al₂O₃ barrier layer performance couldwithstand stresses caused by the folding process. In the optimizedprocess (both extrusion and ALD), permeability values of less than 5g/m2/day with smaller variation, could be achieved.

The measured barrier values in 50% and 90% RH for non-folded and foldedsamples are shown in FIG. 10.

Al₂O₃ ALD Coating Onto PGA Coated Substrates

ALD Al₂O₃ coating was prepared using trimethylaluminium (TMA) and ozoneoxidation, the same recipe that was used for the coating of PLAmaterials. Average as well as minimum and maximum measured WVTR (90%/23°C.) results for non-folded and folded samples are presented in FIG. 11.Results of PGA coated paper and board without Al₂O₃ coatings and alsoPGA board with heat treatment and without Al₂O₃ coating have beenincluded in FIG. 11 to facilitate comparison.

As can be seen in FIG. 11, ALD Al₂O₃ coating onto PGA did notsignificantly improve barrier performance of the samples, especially ifcompared to the barrier level achieved by an oven heat-treatment of PGAcoated board. Also, a relative large variation existed between parallelmeasurements. However, the lowest individual permeability value (0.5g/m2/day) was measured for the 90° folded and Al₂O₃ coated PGA paper.Under these test conditions, Al₂O₃ barrier layer performance couldwithstand folding process stresses well. In an optimized processcomprising both extrusion and ALD, permeability values below 1 withlower variation can be achieved.

The measured barrier values in 50% and 90% RH for non-folded and foldedsamples are presented in FIG. 12.

Example 5—The WVTR Results of Hybrid ALD Coating Onto Extrusion CoatedSubstrates

A hybrid ALD surface comprising two layers was coated on extrusioncoated substrate. The bottom layer was prepared using TMA and ethyleneglycol (EG). A partially organic bottom layer gave elasticity to thewhole ALD layer structure and improve cracking behavior of the topinorganic Al₂O₃ layer which could easily crack. The theoreticalthickness of the bottom layer is 50 nm. The top layer was pure Al₂O₃,prepared using TMA and water as an oxygen source. The top Al₂O₃ layerprovided barrier performance properties of the hybrid structure.

Hybrid ALD Coating Onto PLA Coated Substrates

Average as well as minimum and maximum measured WVTR (90%/ 23° C.)results for non-folded and folded samples are presented in FIG. 13.Results of the PLA coated paper and board without hybrid ALD coatingsare also include in FIG. 13 to facilitate comparison.

Hybrid ALD coating improved the WVTR results compared to samples withoutsuch coating. However, hybrid layer structure showed weaker barrierperformance improvements compared to the single layer Al₂O₃ ALD coating.A relative large variation existed between parallel measurements. As wasthe case of the single layer Al₂O₃ coating, hybrid structure barrierlayer performance could withstand folding process stresses.

The measured barrier values in 50% and 90% RH for non-folded and foldedsamples are presented in FIG. 14.

Hybrid ALD Coating Onto PGA Coated Substrates

Average as well as minimum and maximum measured WVTR (90%/23° C.)results for non-folded and folded samples are presented in FIG. 15.Results of PGA coated paper and board without Al₂O₃ coatings and alsoPGA board with heat treatment and without Al₂O₃ coating are alsoincluded in FIG. 15 to facilitate comparison.

As shown in FIG. 15, coating a hybrid ALD layer onto PGA did not improvebarrier performance of the samples, especially if compared to thebarrier level achieved by an oven heat-treatment of the PGA-coatedboard. However, the hybrid ALD coating had somewhat less variationbetween the parallel measurements compared to the single layer Al₂O₃coating.

The measured barrier values in 50% and 90% RH for not-folded and foldedsamples are presented in FIG. 16.

Example 6—Summary

A paper and board substrate has been provided with basis weights of 80and 237 g/m2, respectively. WVTR was measured in conditions of 50%/23°C. and 90%/23° C. for both materials before any coating treatment inorder to obtain the reference points which can be used as a benchmark inthe assessment of the coating treatment effect in the WVTR performanceof the substrates. Barrier values 1200 and 820 g/m2/day were measured inRH of 90% for paper and board, respectively.

Three different extrusion coating recipes were used for PLA coatings.First coating recipe included only one semi-crystalline PLA (SCP)coating layer, extrusion coated onto base substrates. The second recipecontained two-layer structure, SCP and amorphous PLA (AP) layer, thebottom and the top layer, respectively. Third recipe includesthree-layer structure AP, SC and AP, in bottom to top order. Significantimprovements in barrier properties for all PLA coated materials wereachieved. Barrier values in 90% RH for two- and three-layer PLAstructures after exposed 90° folding process were in the order of 40g/m2/day. The barrier properties did not seem to deteriorate after thefolding process, compared to non-folded samples.

The above is particularly suitable for improving the packaging processof tobacco products. All PLA coated materials can form strong heatsealed bonds in temperature of 130° C., but differences in heat sealingproperties are likely to appear in lower temperatures and shortersealing times. There is room for improving adhesion of the extrusioncoated PLA onto base materials such as paper and board.

PGA coating amounts were 48 and 49 g/m2 for the paper and the board,respectively. A significant improvement in barrier properties for PGAcoated board and paper was achieved. For the PGA coated board and the90° folded samples, WVTR results in 90% RH were around 15 g/m2/day withsome variation. For PGA coated paper, permeability values of less than 2g/m2/day were measured. Because the PGA coated board did not reach thesame low permeability values than the corresponding PGA coated papersamples, it was attempted to improve the permeability properties furtherby one hour oven heat treatment at a temperature of 100° C. Heattreatment improved the WVTR permeability properties of the PGA coatedboard to the same level as in PGA coated paper samples. PGA adhesion inthe base material could be improved by optimizing the parameters ofextrusion coating process (e.g. extrusion temperature). PGA coatedmaterials formed strong heat sealed bonds at a temperature of 130° C.

ALD Al₂O₃ coating was prepared in 100° C. using trimethylaluminium (TMA)and ozone oxidation. The thickness of the Al₂O₃ coating, measured on thesurface of a silicon wafer, was 25 nm. ALD Al₂O₃ thin film on PLA coatedsubstrates significantly improved the WVTR results compared to thesamples without ALD treatment. Al₂O₃ barrier layer performance couldwithstand stresses caused by the folding process. In the optimizedprocess for PLA substrates comprising both extrusion and ALD, barriervalues of less than 5 g/m2/day in 90% RH with small variation could beachieved for ALD Al₂O₃ coated PLA substrates. ALD Al₂O₃ coating onto PGAcoated substrates did not significantly improve barrier performance ofthe samples compared to the PGA coated substrates without ALD coating.However, in the optimized process for PGA substrates comprising bothextrusion and ALD, barrier values of less than 1 g/m2/day with lowervariation could be achieved. In addition, it appeared that the hybridALD coating structure did not bring any barrier performance improvementscompared to single layer ALD Al₂O₃ coating (single layer ALD inorganicfilms such as Al₂O₃ is actually easier for industrial roll-to-rollproduction).

Many modifications and other aspects of the disclosures set forth hereinwill come to mind to one skilled in the art to which these disclosurespertain having the benefit of the teachings presented in the foregoingdescriptions and the associated drawings. Therefore, it is to beunderstood that the disclosures are not to be limited to the specificaspects disclosed and that equivalents, modifications, and other aspectsare intended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

That which is claimed:
 1. A method for making a tobacco packagingmaterial, comprising extrusion coating at least one repulpable polymeronto a paper material to form a polymer layer, wherein the tobaccopackaging material has a water vapor transmission rate (WVTR) that is atleast 90% lower than the paper material.
 2. The method of claim 1,further comprising heat treating the paper material coated with thepolymer layer.
 3. The method of claim 1 further comprising depositing atleast one atomic layer deposition (ALD) layer onto the paper materialcoated with the polymer layer, wherein the ALD layer comprises a metaloxide.
 4. The method of claim 1, wherein the polymer layer comprises apolymer selected from the group consisting of polyglycolic acid (PGA)and polylactic acid (PLA).
 5. The method of claim 1, wherein the papermaterial is coated with at least two polymer layers having differentcrystallinity.
 6. The method of claim 1, wherein the paper material iscoated with about 1-200 g/m² of the polymer.
 7. The method of claim 3,wherein the ALD layer comprises a metal oxide selected from the groupconsisting of Al₂O₃ and SiO₂.
 8. The method of claim 3, wherein the ALDlayer comprises an organic material in addition to the metal oxide. 9.The method of claim 1, wherein the tobacco packaging material has a WVTRof 10 g/m²/day or less at 38° C. and 90% RH.
 10. The method of claim 1,wherein the tobacco packaging material has a WVTR of 3.4 g/m²/day orless at 38° C. and 90% RH.